Bicyclic amidine based catalysts and use in thermosettable compositions

Abstract: Described are novel boron trifluoride complexes with cyclic amidines, which are useful for the conversion of thermosettable compositions. Also described are novel thermosettable compositions incorporating the complexes.

Description: BACKGROUND The present invention pertains to triethylenediamine adducts of certain benzoic acid derivatives and to boron trifluoride complexes with certain bicyclic amidines, and their use as catalysts in thermosettable compositions. Thermosettable compositions are useful in many applications including for example their use as adhesive and coating compositions. Thermosettable compositions are largely based upon epoxy and/or anhydride and/or acid functionality. To prepare the thermosettable composition, the curable resin is blended with one or more catalysts. Depending upon the application, the catalyst can be designed to provide a fairly rapid cure after blending with the resin, or, the curing agent may be designed to provide some measure of latency. That is, the thermosettable resin does not gel over a period of time, e.g. during storage, and only upon heating converts the resin from a liquid (or thermoplastic) state to a tough, hard thermoset solid. Various compositions have been used as catalysts in thermosettable compositions. One group of curing agents includes certain complexes of Lewis acids and amines. For instance, U.S. Patent No. 2,824,083 describes certain amine-BF 3 complexes used as curing agents for polyepoxides. U.S. Patent Nos. 4,933,422 and 4,614,788 describe the use of certain adducts of imidazoles with organic acids having pK a values of 0.5 to 5.0. U.S. Patent No. 2,824,083 describes the use of BF 3 addition products with certain amines, amides, phenol or ether, dissolved in a liquid polyol such as a liquid polyalkylene glycol. U.S. Patent No. 2,839,495 describes the use of the combination of an acid anhydride and a BF 3 complex such as a BF 3 -amine complex to resinify polyepoxides. U.S. Patent No. 3,519,604 describes the use of a polycarboxylic acid anhydride and certain 3- or 4-amino pyridines in combination with a polyepoxy compound to form a curable composition. Japanese KOKAI No. 64-3171A (January 6, 1989) describes certain amino pyridine acid addition salts with dihydroxybenzoic acid derivatives, used as accelerators for curing epoxy resins. Additional background information on catalysts and resins employed in thermosettable compositions can be found in U.S. Patent Nos. 4,816,500 and 4,871,806 and European Patent Application Nos. 90308471.3 (Published February 6, 1991) and 88119031.8 (Published May 24, 1989). SUMMARY OF THE INVENTION The embodiment of the invention provides novel cyclic amidine/boron trifluoride complexes useful in preparing thermosettable compositions. The compounds of this preferred embodiment are boron trifluoride complexes with bicyclic amidine compounds having the general formula: wherein n is a number ranging from 2 to about 11 and R, R', R'' and R"', which may be the same or which may differ from one another, are H or lower alkyl. Still another preferred embodiment of the invention provides a thermosettable composition which comprises a curable resin material and a catalytic amount of a BF 3 /bicyclic amidine complex as described above. Additional preferred embodiments of the invention include processes for preparing the compounds of the invention and for preparing and curing the above-specified thermose table compositions. The invention thus provides compounds that are useful as catalysts in thermosettable compositions, thermosettable compositions, and processes for their preparation and use. Additional embodiments, as well as features and advantages of the invention, will be readily apparent from the following description. The embodiment of the invention includes bicyclic amidine/boron trifluoride (BF 3 ) complexes and thermosettable compositions containing them in catalytic amount. The bicyclic amidine for use in the invention has the formula: wherein n is a number ranging from 2 to about 11 and R, R', R" and R"', which may be the same or which may differ from one another, are H or lower alkyl (i.e. C 1 to C 5 alkyl). 1,5-Diazabicyclo[4.3.0]non-5-ene and 1,8-diazabicyclo[5.4.0]undec-7-ene are especially preferred bicyclic amidines for use in the present invention. The bicyclic amidines for use in the invention may be obtained commercially or may be prepared by techniques known to the art, including for example by the condensation and subsequent cyclization of mixtures of 1,3-propanediamine with pyrrolidone or caprolactam, (see, Hesse, M. et al., Chem. Ing. Tech., 63(10), pp. 1001-1003 (1991)), or by the catalyzed reaction of a lactam with an unsaturated nitrile (see, U.S. Pat. No. 4,943,633). The presence of other, non-interfering substituents on the rings of the bicyclic amidines will be acceptable for the invention and within the general spirit and scope thereof. To prepare the BF 3 /bicyclic amidine complexes, selected bicyclic amidines can be reacted with a suitable BF 3 source so as to provide their corresponding complexes. As an example, a flask can be charged with the bicyclic amidine as a 50 wt% solution in tetrahydrofuran. This solution can be cooled to 15°C, and an equimolar amount of BF 3 etherate added at such a rate that the reaction temperature does not exceed 20°C. The reaction mixture is stirred, e.g. for about one hour. The precipitated white solids can be flltered, washed, and dried. Thermosettable compositions of the invention are prepared by blending a catalyst of the invention, a triethylenediamine adduct or a bicyclic amidine/BF 3 complex, as the case may be, into a curable resin material in the desired catalytic amount, typically about 1 to about 10 weight parts per 100 weight parts of resin. The curable resin material for use in the invention can for example contain epoxy functionality, and/or anhydride functionality and/or acid functionality, and have application in adhesive or coating compositions, among others. Where the catalyst has low solubility in the resin of interest, it is preferred to grind the catalyst to a small particle size prior to blending in order to assist in dispersing the catalyst in the resin. After its preparation, the thermosettable composition will be conventionally employed. The catalysts of the invention may, of course, be used in the thermosettable composition in combination with other conventional additives, for instance curing agents such as phenol-novolac, cresol-novolac and 3,3'-diallyl-4,4'-dihydroxybisphenol A; amine compounds such as 4,4'-methylenebis(2-ethylaniline), 4'4-methylenebis(2,6-diethylaniline) and 4,4'-methylenebis(2-ethyl-6-methylaniline); acid anhydrides such as Nadic Methyl Anhydride (methyl-bicyclo[2.2.1]heptene-2,3-dicarboxylic anhydride), phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, trimellitic anhydride, and pyromellitic anhydride; amide compounds such as dicyandiamide; and dihydrazide compounds such as adipic dihydrazide and isophthalic dihydrazide. Additional conventional additives include dyes, pigments, antioxidants, UV stabilizers, fillers, solvents, reinforcing materials and the like. EXAMPLE I Preparation of Bicyclic Amidine/BF 3 Complexes The bicyclic amidine/BF 3 complexes were prepared as follows. A flask was equipped with a mechanical stirrer, reflux condenser, thermometer and an addition funnel, and was charged with the bicyclic amidine as a 50 wt% solution in tetrahydrofuran. This solution was cooled, using a wet ice bath, to 15°C. An equimolar amount of BF 3 etherate was added, dropwise, at such a rate that the reaction temperature did not exceed 20°C. The reaction mixture was stirred for one hour. The precipitated white solids were filtered, washed with cold tetrahydrofuran and then pentane, and were dried in a vacuum oven at 60°C. The yield of recovered product ranged from 70 to 80%. If a di complex was sought, the same procedure was used except two equivalents of BF 3 etherate were used and the reaction temperature was allowed to increase as the BF 3 etherate was added. The reaction mixture was then heated under reflux for one hour after the BF 3 etherate addition had been completed. The reaction mixture was cooled in a wet ice bath to < 10°C. The reaction mixture was placed on a rotary evaporator and all of the solvents were removed to give an oil. An alternate procedure for making the BF 3 complexes is to dissolve the bicyclic amidine in toluene to give a 50 wt% solution, and cool the solution to 10 to 15°C. An equimolar amount of anhydrous BF 3 is then bubbled into the solution maintaining a reaction temperature of less than 20°C by using a wet ice bath. The reaction mixture is then stirred for 4 hours and the precipitated solids filtered, washed with some pentane, and dried in a vacuum oven at 60°C. Yields for this procedure are 60-65%. Another procedure which can be used to prepare the BF 3 complexes is to dissolve the bicyclic amidine (0.26 mole) in toluene (100 ml) and cool the solution to less than 20°C. To this cooled solution is added BF 3 etherate (0.26 mole), dropwise, holding the reaction temperature at less than 20°C. The reaction mixture is then stirred for one hour, and then heated until a solution resulted. The warm reaction mixture is then placed on a rotary evaporator and the solvent removed under vacuum, at 70°C. The resulting oil slowly solidifies upon cooling. The yields for the procedure are quantitative. The following bicyclic amidine/BF 3 complexes, prepared by the first-specified procedure above, have the following characteristics: DBU-BF 3 , m.p. 86-88, Combustion analysis Actual (theory); C: 48.99 (49.13); H: 7.37 (7.33); N: 12.71 (12.73). DBN-BF 3 , m.p. 123.5-125, Combustion analysis Actual (theory); C: 43.65 (43.79); H: 6.28 (6.30); N: 14.60 (14.59); F: 29.57 (29.69). DBU-2 BF 3 , m.p. N/A, Combustion analysis Actual (theory); C: 41.06 (37.55); H: 6.63 (5.60); N: 7.50 (9.73). EXAMPLE II Testing of Bicyclic Amidine/BF 3 Complexes 1,5-Diazobicyclo[4.3.0]non-5-ene ("DBN") and 1,8-diazabicyclo[5.4.0]undec-7-ene ("DBU") were tested in the same manner as the compounds in Example II. The results are shown in Table 2. Mono-BF 3 Complex with /--Sunshine Gel Time--/ Heat Aged (55°C) Latency Ratio 120 °C 150 °C 3 day 1 day DBU 31.3 8.0 1.03 0.98 DBN 83.7 13.0 1.00 1.0 These results demonstrate the superior latency and reactivity of the bicyclic amidine/BF 3 complexes. In the long term 55°C aging testing, the thermosettable composition containing the DBU-BF 3 complex remained non-gelled for a period of 27 days, while the DBN-BF 3 complex shows a flat viscosity and remains non-gelled for 29+ days. Additionally, using the bicyclic amidine/BF 3 complexes, good quality, light-colored hardened resins were obtained, making these catalysts excellently suited for use in thermosettable coating compositions.

Claims: A compound suitable for use as a catalyst in thermosettable compositions, the compound being a boron trifluoride complex with a bicyclic amidine compound having the formula: wherein n is a number ranging from 2 to about 11 and R, R', R" and R''', which may be the same or which may differ from one another, are H or lower alkyl. The compound of claim 1 in which n is a number ranging from about 3 to about 7 and R, R', R" and R"' are each H. The compound of claim 2 which is a BF 3 complex of 1,5-diazabicyclo[4.3,0]non-5-ene or 1,8-diazabicyclo[5.4.0]undec-7-ene. The compound of claim 3 which is the mono-BF 3 complex of 1,5-diazabicyclo[4.3.0]non-5-ene. The compound of claim 3 which is the mono-BF 3 complex of 1,8-diazabicyclo[5.4.0]undec-7-ene. A thermosettable composition, comprising a curable resin material and a catalytic amount of a boron trifluoride complex with a bicyclic amidine compound having the formula: wherein n is a number ranging from 2 to about 11 and R, R', R'' and R''', which may be the same or which may differ from one another, are H or lower alkyl. The compound of claim 6 in which n is a number ranging from about 3 to about 7 and R, R', R" and R''' are each H. The thermosettable composition of claim 7 which includes a BF 3 complex of 1,5-diazabicyclo[4.3.0]non-5-ene or 1,8-diazabicyclo[5.4.0]undec-7-ene. The thermosettable composition of claim 8 which includes the mono-BF 3 complex of 1,5-diazabicyclo[4.3.0]non-5-ene. The thermosettable composition of claim 8 which includes the mono-BF 3 complex of 1,8-diazabicyclo[5.4.0]undec-7-ene.

Inventors: JOHNSON JOHN R, JOHNSON, JOHN R.
Applicants: REILLY IND INC, REILLY INDUSTRIES, INC.
Application year: 1994
Main classification: C08G59
IPC codes: C08G59